deprecate implicit string casting of mapping keys

Author: xabbuh

Loader/YamlFileLoader.php

@@ -15,6 +15,7 @@
 use Symfony\Component\Translation\Exception\LogicException;
 use Symfony\Component\Yaml\Parser as YamlParser;
 use Symfony\Component\Yaml\Exception\ParseException;
+use Symfony\Component\Yaml\Yaml;
 
 /**
  * YamlFileLoader loads translations from Yaml files.
@@ -39,7 +40,7 @@ protected function loadResource($resource)
         }
 
         try {
-            $messages = $this->yamlParser->parse(file_get_contents($resource));
+            $messages = $this->yamlParser->parse(file_get_contents($resource), Yaml::PARSE_KEYS_AS_STRINGS);
         } catch (ParseException $e) {
             throw new InvalidResourceException(sprintf('Error parsing YAML, invalid file "%s"', $resource), 0, $e);
         }

composer.json

@@ -22,11 +22,12 @@
     "require-dev": {
         "symfony/config": "~2.8|~3.0",
         "symfony/intl": "^2.8.18|^3.2.5",
-        "symfony/yaml": "~2.8|~3.0",
+        "symfony/yaml": "~3.3",
         "psr/log": "~1.0"
     },
     "conflict": {
-        "symfony/config": "<2.8"
+        "symfony/config": "<2.8",
+        "symfony/yaml": "<3.3"
     },
     "suggest": {
         "symfony/config": "",